The present invention relates generally to the gasification of coal in the presence of steam for the production of high quality combustible gases, and more particularly to a method for increasing the decomposition of such steam in the gasifier by adding a water-splitting agent to the gasifier.
The gasification of coal and other carbon-bearing material such a oil shale have been successfully used for the production of fuel or synthesis gas having a sufficient BTU content for use in various industrial applications. The gasification of coal in a typical gasifier is provided by the injection of air, oxygen enriched air, or oxygen, and steam to gasify the coal in the presence of heat for the production of the synthesis gas which is normally formed of carbon monoxide, carbon dioxide, hydrogen and methane. Sulfur present in the coal is also in the gaseous coal gasification products primarily in the form of hydrogen sulfide and is removed prior to using the synthesis gas.
In coal gasification processes steam is often used to increase the efficiency and control the temperature of the process. The steam is also subjected to thermal decomposition for providing additional oxygen and hydrogen to the process to enhance the gasification of the coal and increase the hydrogen content of the gaseous gasification products. The thermal decomposition of steam in a coal gasifier is most efficient at temperatures above 2300.degree. F., however, most gasifiers are normally operated at a temperatures below 2300.degree. F. so that in such steam-aided gasification processes only about 35 to 40 percent of the steam is decomposed to hydrogen and oxygen. Decomposition of a greater percentage of the steam in the gasifier would significantly improve the efficiency and cost effectiveness of the coal gasification process especially in the reduction of external oxygen generation in oxygen-blown gasifiers.